DOES POPULATION DENSITY AND HUMAN ACTIVITIES AFFECT THE RATE OF REDUCTION OF FUKUSHIMA DAICHI RADIATIONS?


This study uses Nihommatsu city and Mimanisoma City as case studies. The two cities are 70km and 30km from Fukushima Daichi Plant respectively.

Part I: Nihomatsu City,70km to Fukushima Daichi

1.1 Required Packages
library("leaflet")
library(readr)
library(dplyr)
library(RColorBrewer)
library(Hmisc)
library(ggplot2)

NB:Important Notes from the Nuclear Regulation Authority on JAEA website

Purposes of this vehicle survey were: 1. To ascertain the tendency and cause of time change of air dose rates by comparing past vehicle survey data and survey meter data at the height of 1 m above ground as well as “walk survey” data, and 2. To contribute to the establishment of radioactive substances distribution prediction model. MEXT evaluated the decrease in the air dose rates caused by the decay of cesium during the survey period and it was around 1%, which was smaller than the errors of measuring instruments source

1.2 Loading June 2011 Fukushima Data and selecting Nihomatsu’s.
niho <- read_csv("jun_2011_fukushima.csv")
niho2013 <- read_csv("nov_2013_fukushima.csv")
# View(niho2013)
# names(niho)
dim(niho)
## [1] 45273    18
# head(niho)
class(niho)
## [1] "tbl_df"     "tbl"        "data.frame"


##### 1.3 Change to machine readeable column names

names(niho) <- c("gridcode","pref","city","gridCenterNorthlat","gridCenterEastlng","gridCenterNorthlatDec",
                 "gridCenterEastlngDec","daichi_distance","no_samples","AvgAirDoseRate",
                       "NE_nLat","NE_eLong","NW_nLat","NW_eLong",
                       "SW_nLat","SW_eLong","SE_nLat","SE_eLong")
names(niho2013) <- c("gridcode","pref","city","gridCenterNorthlat","gridCenterEastlng","gridCenterNorthlatDec",
                     "gridCenterEastlngDec","daichi_distance","no_samples","AvgAirDoseRate",
                     "NE_nLat","NE_eLong","NW_nLat","NW_eLong",
                     "SW_nLat","SW_eLong","SE_nLat","SE_eLong")
#Strip Nihommatsu city,
niho$city[niho$city == "Nihommatsu city"] <- "nihommatsu"
niho2013$city[niho2013$city == "Nihommatsu city"] <- "nihommatsu"


##### 1.4 Filter nihommatsu observerations

nihom <- subset(niho, city == "nihommatsu")
nihom2013 <- subset(niho2013, city == "nihommatsu")
dim(nihom)
## [1] 2944   18
dim(nihom2013)
## [1] 11758    18
# View(nihom2013)
class(nihom)
## [1] "tbl_df"     "data.frame"


##### 1.5 Create air dose quantiles that are plot-able,i.e 6 categorical variables.

niho_q <- nihom %>%
        mutate(dose_quants = cut2(nihom$AvgAirDoseRate,cuts=c(0.1,0.5,1.0,1.5,2.0,2.5,3.0),levels.mean=TRUE))
# View(niho_q)
niho_q <- na.omit(niho_q)
# write_csv(niho_q, path = "niho_q.csv")
nihom2013_q <- nihom2013 %>%
        mutate(dose_quants = cut2(nihom2013$AvgAirDoseRate,cuts=seq(0.06,1.6,0.25),levels.mean=TRUE))
summary(nihom2013$AvgAirDoseRate)
##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##  0.0630  0.2800  0.3700  0.4009  0.4900  1.4000
summary(niho_q$AvgAirDoseRate)
##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##   0.190   0.710   1.000   1.029   1.300   2.500
  • Visible reduction of Average Air Dose Distribution by half in Nihomatsu.
  • Trouble is knowing the distribution of causes of this reduction?
1.6 Color function
iro <- colorFactor(
        palette = "YlOrRd",
        domain = niho_q$dose_quants
)
iro2013 <- colorFactor(
        palette = "YlOrRd",
        domain = nihom2013_q$dose_quants
)
# Link of Daichi
fukulink <- paste(sep = "<br/>",
                  "<br><a href='http://www.tepco.co.jp/en/decommision/index-e.html'>Fukushima Daichi</a></b>",
                  "Source of radiations"
)


1.7 Nihomatsu Average Air Dose Rate for 2011
niho_plot <- leaflet() %>%
        addTiles()%>%
        addRectangles(data = niho_q,lng1 = ~SW_eLong, lat1 = ~SW_nLat,lng2 = ~NE_eLong, lat2 = ~NE_nLat,
                      color = ~iro(niho_q$dose_quants))%>%
        addLegend("bottomright", pal = iro, values = niho_q$dose_quants,
                  title = "AvgAirDoseRates",
                  labFormat = labelFormat(prefix = "µSv/h "),
                  opacity = 1)%>%
        addPopups(lat = 37.4211, lng = 141.0328,popup = fukulink,
                  options = popupOptions(closeButton = TRUE)) 
niho_plot


1.8 Nihomatsu Average Air Dose Rate for 2013
niho2013_plot <- leaflet() %>%
        addTiles()%>%
        addRectangles(data = nihom2013_q,lng1 = ~SW_eLong, lat1 = ~SW_nLat,lng2 = ~NE_eLong, lat2 = ~NE_nLat,
                      color = ~iro2013(nihom2013_q$dose_quants))%>%
        addLegend("bottomright", pal = iro2013, values = nihom2013_q$dose_quants,
                  title = "AvgAirDoseRates",
                  labFormat = labelFormat(prefix = "µSv/h "),
                  opacity = 1)%>%
        addPopups(lat = 37.4211, lng = 141.0328,popup = fukulink,
                  options = popupOptions(closeButton = TRUE)) 
niho2013_plot


1.9 Nihommatsu 2011, Counts of Measuring Locations per Air Dose Rate
ggplot(niho_q, aes(daichi_distance,AvgAirDoseRate)) +
        geom_point() +
        geom_smooth(se = FALSE)+
        ggtitle("AvgAirDose against Distance to Daichi Plant")


##### 1.91 Nihommatsu 2011,Counts of Measuring Locations per Air Dose Rate

ggplot(data = niho_q) +
        geom_bar(mapping = aes(x = daichi_distance, fill = dose_quants), width = 1)+
        ggtitle("AvgAirDose Measured Counts against Daichi Distance")


### PART II: Minamisoma City, 30km to Fukushima Daichi

mina <- read_csv("niho.csv")
dim(mina)
## [1] 45273    18
# View(mina)


##### 2.1 Change to machine readeable column names

#change Minamisoma city to minamisoma
mina$city[mina$city == "Minamisoma city"] <- "minamisoma"
#filter nihomatsu observations only
mina <- subset(mina, city == "minamisoma")
dim(mina)
## [1] 1985   18
summary(mina$AvgAirDoseRate)
##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##   0.210   0.520   0.780   1.771   1.800  18.000
#plot(mina$AvgAirDoseRate)


2.2 Create air dose quantiles that are plot-able,6 categorical variables.
mina_q <- mina %>%
        mutate(mina_quants = cut2(mina$AvgAirDoseRate,cuts=seq(0.2,20,2.2),levels.mean=TRUE))
## View(mina_q)
mina_q <- na.omit(mina_q)
write_csv(mina_q, path = "mina_q.csv")


2.3 Color function
mina_iro <- colorFactor(
        palette = "Set1",
        domain = mina_q$mina_quants
)


2.4 Minamisoma Average Air Dose Rate for 2011
mina_plot <- leaflet() %>%
        addTiles()%>%
        addRectangles(data = mina_q,lng1 = ~SW_eLong, lat1 = ~SW_nLat,lng2 = ~NE_eLong, lat2 = ~NE_nLat,
                      color = ~mina_iro(mina_q$mina_quants))%>%
        addLegend("bottomright", pal = mina_iro, values = mina_q$mina_quants,
                  title = "AvgAirDoseRates",
                  labFormat = labelFormat(prefix = "µSv/h "),
                  opacity = 1)%>%
        addPopups(lat = 37.4211, lng = 141.0328,popup = fukulink,
                  options = popupOptions(closeButton = TRUE)) 
mina_plot


2.5 Minamisoma AvgAirDose against Distance to Daichi Plant
ggplot(mina_q, aes(daichi_distance,AvgAirDoseRate)) +
        geom_point() +
        geom_smooth(se = FALSE)+
        ggtitle("AvgAirDose against Distance to Daichi Plant")


2.6 Minamisoma 2011, Counts of Measuring Locations per Air Dose Rate
ggplot(data = mina_q) +
        geom_bar(mapping = aes(x = daichi_distance, fill = mina_quants), width = 1)+
        ggtitle("Counts of Measuring Locations per Air Dose Rate")

PART III: Calculating the Coefficient of Reduction

3.1 Merging 2011 and 2013 Nihomatsu Data Sets
library(ggplot2)
niho_q <- read_csv("niho_q.csv")
niho2013_q <- read_csv("niho2013.csv")
names(niho_q) <- c("gridcode","pref","city","gridCenterNorthlat","gridCenterEastlng","gridCenterNorthlatDec",
                 "gridCenterEastlngDec","daichi_distance","no_samples","AvgAirDoseRate2011",
                       "NE_nLat","NE_eLong","NW_nLat","NW_eLong",
                       "SW_nLat","SW_eLong","SE_nLat","SE_eLong")
names(niho2013_q) <- c("gridcode","pref","city","gridCenterNorthlat","gridCenterEastlng","gridCenterNorthlatDec",
                     "gridCenterEastlngDec","daichi_distance","no_samples","AvgAirDoseRate2013",
                     "NE_nLat","NE_eLong","NW_nLat","NW_eLong",
                     "SW_nLat","SW_eLong","SE_nLat","SE_eLong")
niho11_13 <- merge(niho_q, niho2013_q, by.x = "gridcode", by.y = "gridcode", all = TRUE)
# View(niho11_13)
# Check if the merged columns are real identical
niho11_13 <- na.omit(niho11_13)
identical(niho11_13$gridCenterNorthlat.x,niho11_13$gridCenterNorthlat.y)
## [1] TRUE
identical(niho11_13$daichi_distance.x,niho11_13$daichi_distance.y)
## [1] TRUE
identical(niho11_13$no_samples.x,niho11_13$no_samples.y) #2011 and 2013 samples differ,but lets ignore that.
## [1] FALSE
niho11_13 <- select(niho11_13,gridcode,pref.x,city.x,gridCenterNorthlat.x,gridCenterEastlng.x,gridCenterNorthlatDec.x,
                 gridCenterEastlngDec.x,daichi_distance.x,no_samples.x,AvgAirDoseRate2011,
                       NE_nLat.x,NE_eLong.x,NW_nLat.x,NW_eLong.x,no_samples.y,AvgAirDoseRate2013)
# create new data set (niho11_13)
write_csv(niho11_13,path = "niho11_13.csv")
niho11_13 <- read_csv("niho11_13.csv")
#View(niho11_13)
#Compare AvgAirDoseRate of 2011&2013
plot(x=niho11_13$AvgAirDoseRate2011,type="l",col="red",ylab = "Avg Air Dose Rate",xlab = "Frequency of measuring",main = "Compare AvgAirDoseRate of 2011&2013 Nihomatsu")
lines(niho11_13$AvgAirDoseRate2013,col="green")
legend("topright", legend = c("AvgAirDoseRate2011","AvgAirDoseRate2013"))

#Frequency
3.2 Developing a Linear Model

Linear Model \[Y{i} = \beta_{0} + \beta_{1} X_{1i} + \beta_{2} X_{2i} + \beta_{3} X_{1i} X_{2i} + \epsilon_{i}\]
Mr Sato Tetsuro’s Hypothesis \[AvgAirDoseRate = \beta_{0} + \beta_{1} daichi distance + \beta_{2} popn density + \beta_{3} human activities + \beta_{4}(popn density)(human activities) + \epsilon_{i}\]

Assumptions:
  1. The above linear model only looks at 3 parameters hypothesised to affect Air Dose Rate reduction.
  2. Effect of Air Dose Rate reduction due to the Time series nature of radiations’ half life is assumed constant as measured by MEXT.


3.21 Air Dose Rate Reduction due to Distance to Daichi Plant
fit1 <- lm(AvgAirDoseRate2013~daichi_distance.x, data = niho11_13)
summary(fit1)
## 
## Call:
## lm(formula = AvgAirDoseRate2013 ~ daichi_distance.x, data = niho11_13)
## 
## Residuals:
##      Min       1Q   Median       3Q      Max 
## -0.27317 -0.10516 -0.02457  0.07873  0.89017 
## 
## Coefficients:
##                     Estimate Std. Error t value Pr(>|t|)    
## (Intercept)        0.5844396  0.0200218   29.19   <2e-16 ***
## daichi_distance.x -0.0049126  0.0003721  -13.20   <2e-16 ***
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## Residual standard error: 0.1373 on 2805 degrees of freedom
## Multiple R-squared:  0.0585, Adjusted R-squared:  0.05817 
## F-statistic: 174.3 on 1 and 2805 DF,  p-value: < 2.2e-16
confint(fit1)
##                          2.5 %       97.5 %
## (Intercept)        0.545180562  0.623698590
## daichi_distance.x -0.005642192 -0.004182925


3.22 Air Dose Rate Reduction due to Population Density
Challenge

The Air Dose Rate measurements were collected from three sources:

  • Cars and Buses with Sensors: Measure Air of 100sq meters from the road
  • Un manned Auto Helicopter: Measure from 300m above ground
  • Fixed Sensors: Geographically sparsed


3.23 Air Dose Rate Reduction due to Human Activities
Challenge

What constitutes Human Activities?:

  • Farming: Short life span crops lead to frequent land tilling
  • Cleaned Places: Parks, GolfCourses, Gardens are cleaned too and could reduce radiations

to be continued